* Engine Management System (EMS): The computer and wiring harness controlling the engine may be incompatible. The 2005 model year likely has a different ECU (Engine Control Unit) and potentially different sensors. This is the biggest hurdle. You'd likely need to swap the entire wiring harness as well.
* Sensors and Actuators: Minor differences in sensors (oxygen sensors, crankshaft position sensor, etc.) or actuators (throttle body, etc.) might exist.
* Minor Mechanical Differences: There might be subtle changes in the engine's design over the model years that could create compatibility issues, though this is less likely than the EMS differences.
* Transmission Compatibility: Ensure the transmission is compatible. While the transmission type is likely the same, there might be subtle differences that would prevent a perfect fit.
In short, while the engines are *similar*, you'd need to carefully compare the engine codes (found on an identification plate on the engine itself) and consult a repair manual for both years to ascertain compatibility. Simply swapping the engine is unlikely to be successful without significant modification and potentially re-wiring. It's far more likely to be easier and cheaper to find a used 2.4L engine from a similar year to the 2001 model.
